This invention relates to an apparatus for cleaning soft hydrophilic gel contact lenses, commonly termed soft contact lenses. More particularly, the invention relates to an apparatus for cleaning soft contact lenses by the application of an electrical field through a moistened medium that is in contact with one or more soft contact lenses. The invention removes the accumulated lens contaminants by the electrically-induced migration of the contaminants from the surface and out of the body of the lens.
Soft contact lenses are porous films which may be made of a variety of materials and which are used, generally, to correct for defects in vision. Foreign substances, however, may accumulate on the surface of the lenses or may be absorbed within the body of the lenses. Contamination is a problem which confronts all wearers of soft contact lenses. The contaminants come from a variety of sources. For example, the atmosphere contains a variety of organic and inorganic substances which may act to contaminate soft lenses. Handling of the lenses places microscopic deposits on the surface of the lenses. The tears which constantly bathe the lenses contain a variety of organic and inorganic molecules which can be selectively absorbed from the tears onto and within the soft lenses.
Lens accumulations may provide a suitable substrate for other compounds such as preservatives or organisms (e.g., bacteria, fungi, and yeasts) which, but for the accumulations, may not have become associated with the lens.
Lens deposits can adversely affect the optical performance of the lens. It is known that the rate of contaminate deposition is, in part, a function of the actual wearing time of the lenses. After some period, deposits may appear as a white, partially opaque layer or as a clear, transparent layer, with or without color, which covers all or part of the lens. With increased lens opacity, visual acuity is decreased. Lens deposits will also alter the optical characteristics of the lenses.
Besides affecting the optical performance of the lens, the contamination of a soft contact lens can also affect the physiology of the eye. Increased irritation, "red eye", and conditions such as allergic conjunctivitis or giant papillary conjunctivitis may also be produced by a contaminated lens.
To maintain the physical and optical characteristics and performance of their lenses, users normally must remove the deposits and then sterilize the lenses to kill bacteria and other microorganisms which reside on the surface of and within the lenses. This regime must be followed on a regular, often daily basis.
Conventional cleaning apparatus utilize a variety of physical and chemical techniques. Physical cleaning techniques include scrubbing methods, agitation methods, and swirling methods. Chemical techniques consist of the use of surfactant cleaners, oxidizing agents, and enzyme cleaners, among others.
A variety of patents teach specific physical or chemical solutions to the problem of removing unwanted lens deposits. As to removal of the contaminants by physical methods, the following rely entirely or partially on such methods: U.S. Pat. No. 4,607,652 (application of ultrasonic frequency mechanical vibrations); U.S. Pat. No. 4,582,076 (rotation of lens to enhance cleansing action); U.S. Pat. No. 4,559,662 (scrubbing apparatus); U.S. Pat. No. 4,444,307 (agitation and swirling apparatus in part performed by impellers); U.S. Pat. No. 4,187,574 (scrubbing means); and U.S. Pat. No. 3,871,395 (use of high ultrasonic frequency).
As to chemical methods to remove lens contaminants, the following rely in whole or in part on such methods: U.S. Pat. No. 4,609,493 (contact lens cleaning preparation comprising, in part, of an enzyme with proteolyic activity, a surfactant, and anionic dissociating compounds); U.S. Pat. No. 4,096,870 (cleaning by pancreatin); and, U.S. Pat. No. 3,908,680 (use of an acidic solution and basic solution).
Conventional cleaning apparatus which utilize these techniques, however, may be ineffective or may harm the lenses. For example, physical cleaning techniques may abrade the surface of the lens and thereby impair the optical performance of the lens. Chemical cleaners, such as surfactants, may be ineffective because they may not remove all contaminants or be undesirable because a chemical deposit may remain on the lens at the completion of the cleaning. Strong oxidizing agents, such as persulfates, perborates, or even hypochlorite bleaching agents may remove films but often with irreversible damage to the lens. Enzyme cleaners and calcium-chelating solutions may remove certain components of the film but must be used regularly.